SCP-1026 has displayed several previously unknown abilities during Incident 1026-1. These abilities included enhanced strength and speed, camouflage (SCP-1026's body turned partially invisible to observers), and limited shape-changing abilities (SCP-1026 managed to fit through a 3-inch wide gap left by a closing door). SCP-1026 also displayed a remarkable resistance to gunfire; surviving personnel reported that bullets appeared to pass through its body without harming it.

This reminds me of a list of super powers on a comic book wiki. Downvoted

If it is memetic, that means that the entity presents some sort of information that the viewer perceives as [insert your loved one here] and then they act accordingly. Although that should also (but not necessarily) mean that photos and videos of the thing would not be blurry, the viewer could still interpret that visual stimuli as "this is a person important to me" — but maybe there's something about the thing that photos and videos don't pick up. That's fine. But that also means that you can really easily tell what this thing actually is by holding up a digital camera and watching the live recording of it instead of watching it directly. It would also probably mean that if it was in a sealed room with a window and the only exposure is looking at it through glass then it's a blurry non-person instead of the person who looks and sounds and smells just like your mother or wife or whatever.

If it is memetic that means the entire effect is based on how people interpret what it is, as opposed to it magically changing its perception in someone's mind. Memes are information, not telepathy.

But that also means that since this thing is not directly affecting people, the effect should not always be the same. A lot of our D-class are sociopaths (so they say) so who is to say that they have ANY loved ones at all? Maybe there's some monster D-class out there who interprets the [insert loved one here] effect by seeing the little girl with the cutest screams? What would an emotionless person with no personal connections see?

Glass doesn't have any affect on 1026's ability, presumably because glass allows light directly through it, whereas a screen just reproduces what it receives.

Humans can't be completely emotionless, but extreme sociopaths don't notice the entity at all and refuse to acknowledge its existence. Non-humans and some humanoid SCPs (such as Able), see its "true" form.

I don't like it. It's overpowered, very overpowered, and can reproduce with unknown speed. 173 is weaker than this, and yet when it begun to reproduce it lead to XK fairly quickly. And yet it's Euclid.

And the basic idea I don't like too. It was done better in 268. There it's just mentioned in passing and then it's all about an awesome super-thing that exist in a way what we puny mortals can't even comprehend outside of time and space.

A being that exists outside of time and space can time travel and teleport at will. This one can't.